Geological Drive – Ventura Basin

I-5/SR-14 Interchange to Magic Mountain Pkwy via I-5

Starting on I-5 at the Balboa Blvd. Bridge, Mark your Odometer HERE. Driving along I-5, you begin to enter Newhall Pass. This is a fairly low pass but one of great importance. Through here pass Interstate 5, State Route 14, Union Pacific Railroad and Metrolink.

This is the gateway to the north for Los Angeles. At 1.1 miles, you pass below the bridge that collapsed in the 1994 Northridge earthquake. This pass is a very active seismic area. Many of the aftershocks from that quake originated here. The Santa Susana Thrust Zone and the Foothill Thrust Zone meet here. These faults are partially responsible for raising these mountains. About 0.5 miles up on SR-14, you can see a thrust fault. It is a part of the Beacon Thrust Fault.

View of Beacon Thrust Fault along Highway 14.

Continuing along, At 2.1 miles you can see the Pico Formation. This formation was deposited in a shallow sea about 5 million years ago during the Pliocene Epoch. These deposits are very fossiliferous. You may also notice that these deposits form large bluffs. The bluffs are composed of more resistant sandstones and conglomerates. It was these same deposits that made travel through here very difficult in the days before modern highways were constructed through here. If you would like to get off the freeway and view these fossils and deposits up close, get off at Calgrove Blvd.

At 4.1 miles, you reach Calgrove Blvd. If you plan to get off the freeway here, note the distance on you odometer. [Side Trip Begins] At the stop sign, turn left. Continue under the bridge and turn at the next right. On the left hand side of the road, there is a large cut in the hill. Stop on the right side of the road just after this cut. This cut is a great exposure of the fossils that the Pico Formations contains and is a good spot to look at the boundary of the Pico and Saugus Formation. Looking to the west, there is a small canyon with houses. On the right side of the canyon, there are many bluffs. On the left side of the canyon, the topography is much more subdued. This is caused by the Saugus Formation. It is not a very strong formation. It was deposited about 2 million years ago by streams eroding down the surrounding mountains. Return to I-5 [Side Trip Ends].

Continuing on I-5, you pass by the western edge of Santa Clarita. At 6 miles, to you left you get a view of more of the Pico topography in Pico Canyon. At 6.3 miles, you get a nice view of the Saugus Formation and the Castaic Formations in the mountains ahead of you. You can see from here that the Saugus Formation is folded and highly eroded. At 8 miles, you can see what sort of topography generally prevails in areas where the Saugus Formation exists. Nicely rounded hills and low relief prevail here. You are now on a downhill slope towards the Santa Clara River. At 9 miles, you reach the exit for Magic Mountain. This is the end of this trip.

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A few months ago, I decided to purchase a new domain in the anticipation of moving to northern California. Whether or not that move takes place, I still own that domain. As such, this site may be expanding in scope to cover a few more counties. The new site, NorCalRegion.Com, is still a work in progess, but will cover highways and geology in the northern half of the state. Where that line will be drawn is still being worked out. Look for updates in the coming months for these changes and expansions.

There is a group in Bakersfield trying to get historic route signs posted on the original alignment of US 99 through the Bakersfield area. They could use your support. Check out the site below for more information.

Los Angeles County Department of Public Works has a wealth of information available on their website. With a bit of patience and some looking around, you can find quite a few treasures using their mapping application. I’ve so far found the original survey data for the “Bridge To Nowhere” roadway, plans for other roadways that were never built in the Sierra Pelona Mountains, as well as the forest service permit for the Shoemaker Canyon Road that was never completed.